Because then we would know, "officially" that there is inflation. Now, anyone who buys regular stuff, gas for car, food for table; knows that there is inflation. But, govt. doesn't want you to know about inflation, so they use numbers that don't actually relate to how people live their lives. Voila! No inflation. And, a compliant and corrupt media just reports it as "facts".
That is because entitlements and Social Security are mandated to increase if the C.O.L. increases.
If you don't include things like food and gas in the C.O.L. figures you can get away with not increasing Social Security and Entitlement payouts...
“Butter Prices Reach All-Time High Amid Smaller Stockpiles”